Sight glass follow up

jermfab · Apr 22, 2018

I made mention of cracking the oil sight glass on my lathe last week. The helpful PM community steered me towards several places, but good ol’ eBay was the one that came through.
My lathe uses a press-in style sight glass as opposed to (what appears to be) the more common NPT or BST threaded sights. The sight glass hole finishes at .875, ironically just undersized for a 3/4” NPT tap. Both the apron and headstock take this same oil glass.
My question: on a scale of one to absolutely stupid, how foolish is the idea of reaming these holes to the 57/64” size for a 3/4” NPT tap and threading these holes?

I like the idea of having the maximum parts availability, always. Additionally, if I tap the parts for 3/4” NPT and have another freak accident I can at least plug the hole with a readily available pipe plug and the machine isn’t DOWN. Conversely there are all the issues with introducing cast iron chips into the lubrication system...

Anyhow, hoping someone older and wiser than myself will chime in with their $.02.

Thanks all

Jeremy

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dalmatiangirl61 · Apr 22, 2018

I thought you needed the 3/4"npt type plug, not sure I have seen a plastic push in type that was oil tight, but ain't seen everything. Assuming oil is already drained, can you remove lid to access? Put a big magnet inside gearbox, drill/tap, remove magnet and insert plug. That is what I would be tempted to do.

TDegenhart · Apr 22, 2018

dalmatiangirl61 said:
I thought you needed the 3/4"npt type plug, not sure I have seen a plastic push in type that was oil tight, but ain't seen everything. Assuming oil is already drained, can you remove lid to access? Put a big magnet inside gearbox, drill/tap, remove magnet and insert plug. That is what I would be tempted to do.

You won't get all the chips out that way, there will be small ones that will bridge between the magnet and casting. I can't think of a positive way to get chips out except by emptying the cavity and then cleaning the chips with a vacuum or similar (not an air gun!).

Tom

dgfoster · Apr 22, 2018

TDegenhart said:
You won't get all the chips out that way, there will be small ones that will bridge between the magnet and casting. I can't think of a positive way to get chips out except by emptying the cavity and then cleaning the chips with a vacuum or similar (not an air gun!).

Tom

Do you need to get the chips out? I figure they just settle into the bilge and stay there. The commonly-used Non-detergent oil helps the smallest ones settle out. I suppose you could push a small neodymium magnet down into the bottom of the headstock to actively grab tiny bits out of solution.

Denis

thermite · Apr 23, 2018

TDegenhart said:
You won't get all the chips out that way, there will be small ones that will bridge between the magnet and casting. I can't think of a positive way to get chips out except by emptying the cavity and then cleaning the chips with a vacuum or similar (not an air gun!).

Tom

Trick is to not let them IN to begin with.

Plug the back end with paper daubed in plaster, RTV it. Grab a rubber ball off a kid's toy, synthetic wine cork.... wotever.

Fill cavity with grease.

As the tap proceeds the grease carries the chips out. Clean up. Thoroughly. Plug allows fluid flush, bit of air, etc.

THEN pull the plug out toward yah. You DID remember to embed a loop, wire, or cord into it, yah?

Marine Engineer Uncle said they'd use a fairly large "cup" outside the hull, seal it. Do a through-hull fitting essentially "in the dry" even well below waterline, Seal the fitting. Remove the cup. Low risk. Not even much seawater in the work area.

Similar principle here if the sight glass is in thinwall. Does need access, etc. but humans are an inventive lot as to adapting ideas.

When they need to be.

jermfab · Apr 23, 2018

I’ve got good access to both sides of the casting. In addition the point where the sight glass mounts is a low point and should grab any chips before they have a chance to make their way into the head stock. Damming the back side was an idea I’d had as well as using either soft wax or grease as a cutting lubricant to hold the chips on the tap instead of letting them fall into the headstock. Then vacuum the inside, magnet, vacuum until I’m satisfied there aren’t any errant chips.

I’m still wondering if this is a good idea. I’m on board with all of your suggestions of HOW to tap the headstock, would still like someone to chime in as to whether it’s a not terrible idea or a really bad one...

Thanks again

Jeremy

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TDegenhart · Apr 23, 2018

I know nothing about the sight glass, is it a plain cylinder or is it threaded? How were you thinking of mounting it?

Tom

Mark Rand · Apr 23, 2018

When I got my 1952 Hardinge HLV, the apron sight glass was buggered (as well as the entire contents of the apron gearbox). That was also a press in type. It's not really that hard to turn a replacement. You can use Loctite if you aren't confident about turning close enough for a press fit. I used a bit of glass from a broken picture frame, cut a circle with a glass cutter, then pressed it between two bits of bar in a lathe, with the pressure supplied by a rotating centre. Thus mounted, I trimmed it to the right diameter and a clean edge using a diamond abrasive block. The internal parts (glass, spacer, rear plade with scribed line, vent and drain holes and a locating ring, were all stuck in with Loctite. Then the assembly (turned half a thou oversize) was pressed into the hole in the Apron front plate.

jermfab · Apr 23, 2018

Existing sight glass is a press-in affair that I’ve had a fairly difficult time finding a replacement for. The aftermarket is rife with oil sight glasses threaded for either NPT or BST.
My thought process is this:
Freak accident or not, the headstock sight glass is in a relatively vulnerable spot.

The hole and the original sight glass measure .875”

I managed to find metric press-in sight glasses at 22.5mm, slightly larger than my hole, but I think I can make it work.

Looking forward to potentially replacing this piece again, I’m wondering if it makes sense to go ahead and thread the lathe to accept the much more readily available 3/4” NPT threaded parts? While the original (I assume) sight glass has lasted for nearly forty years I managed to put the end of a chuck wrench through it. Additionally, if I do happen to damage the sight glass again I can plug the hole with a pipe plug and keep on working. Right now my lathe is down until the replacement parts arrive. There’s my dilemma and my thinking on it.

Jeremy

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dgfoster · Apr 23, 2018

jermfab said:
Existing sight glass is a press-in affair that I’ve had a fairly difficult time finding a replacement for. The aftermarket is rife with oil sight glasses threaded for either NPT or BST.
My thought process is this:
Freak accident or not, the headstock sight glass is in a relatively vulnerable spot.

The hole and the original sight glass measure .875”

I managed to find metric press-in sight glasses at 22.5mm, slightly larger than my hole, but I think I can make it work.

Looking forward to potentially replacing this piece again, I’m wondering if it makes sense to go ahead and thread the lathe to accept the much more readily available 3/4” NPT threaded parts? While the original (I assume) sight glass has lasted for nearly forty years I managed to put the end of a chuck wrench through it. Additionally, if I do happen to damage the sight glass again I can plug the hole with a pipe plug and keep on working. Right now my lathe is down until the replacement parts arrive. There’s my dilemma and my thinking on it.

Jeremy

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f

One other way to skin the cat: make a pipe-threaded ID but smooth O.D. insert whose O.D. fits the present hole. Clean hole with alcohol and permanently Loctite insert in place. No chips to worry (needlessly?) about and easy replacement with a little smaller but readily available sight glass next time. You can get by with a pretty thin wall on the insert as it is well supported.

Denis

thermite · Apr 23, 2018

jermfab said:
The aftermarket is rife with oil sight glasses threaded for either NPT or BST.

You've hit "overthink" on all this. At the outset, actually.

The fittings industry in general also has goods wherein a nut and elastomeric seal - O-ring, washer, wotever - go inside on a nipple, reducer, coupling or bushing, and are matched on the other side of the bulkhead or wall. Place it, tighten the nuts to make the seal. Select a sight glass to fit it. Or use a sight glass wherein a washer or O ring will do the same thing, no extra parts. Have to lift the gearbox lid to change to a new one? BFD.

Raid the local Big Box, brass fitting subsection of plumbing, you may not even have to place an online order.

Lube oil under low pressure, no pressure, nor even rather HIGH pressure does not require a metal-to-metal seal.

readymix · Apr 23, 2018

I usually buy the press in sights from Oil windows, oil window, oil level window, oil level windows, sight glass, sight glasses

They might have what you need

dalmatiangirl61 · Apr 23, 2018

I would drill and tap it for 3/4 npt. Why? Because I like secure fittings, if it ever breaks again you can just plug it, and in that location I would want it as flush as possible.

Richard King · Apr 24, 2018

I would prefir you turn a ring and press it in and use a smaller dia. Sigthglass that way there no chance chips would fall inside headstock
You my also call some of the lathe importer distribtor as they may stock the metric one.

jermfab · Apr 28, 2018

The metric sightglass(es) I ordered came in Thursday. They’re too small... Since the headstock isn’t under pressure I figured several wraps of electrical tape would fill the gap long enough to use the lathe for a better solution.
As I can always thread the headstock, but cannot un-thread it I’ve chosen to exhaust other options first.
So, I made this adapter from some aluminum and one of the remaining metric sight glasses.

It’s certainly not the most elegant solution and may not work any better than wraps of electrical tape, but at least I haven’t modified anything in any irreparable way.

Jeremy

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petryss · Oct 18, 2020

I have the same problem with my Clausing Colchester 15 x 50. I am in the process of rebuilding. I have 3 (1-1/4") OD sight glasses. I can Conceivably thread the one in the front gearbox cover and the one in the apron housing but no way to thread the one in headstock housing. Mine were all push in. I missed the first part of this thread. Will the members that posted ideas where to get the push in please post that info again?

dalmatiangirl61 · Oct 18, 2020

IIRC McMaster, and probably other places, have 1-1/4" press in sight glasses. I know this because I recently needed 1-1/8" sight glass, which is not available.

petryss · Oct 18, 2020

I just found this on a google search. Home | JW Winco Standard Parts go to search and type in EN545

dalmatiangirl61 · Oct 18, 2020

petryss said:
I just found this on a google search. Home | JW Winco Standard Parts go to search and type in EN545

That just might work! Thank you!

Sight glass follow up

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